Automatic planetary automotive transmission



April 1939. F. w. COTTERMAN 2,154,419

AUTOMATIC PLANETARY AUTOMOTIVE TRANSMISSION Original Filed, Jan. 20, 1936 5 Sheets-Sheet l April 18, 1939. F. w. COTTERMAN 2,154,419

AUTOMATIC PLANETARY AUTOMOTIVE TRANSMISSION Origj nal Filed Jan. 20, 1936 5 Sheets-Sheet 2 April 18, 1939. F W. COTTERMAN AUTOMATIC PLANETARY AUTOMOTIVE TRANSMISSION Original Filed Jan. 20, 1936 5 Sheets-Sheet 3 om st R m3 on g &

7M W KmM April 18, 1939. F. w. COTTERMAN 2,154,419

AUTOMATIC PLANETARY AUTOMOTIVE TRANSMISSION Original Filed Jan. 20, 1936 5 Sheets-Sheet 4 //IIIIIIIIIM% 1 N INVENTOR.

April 18, 1939. F. w. COTTERMAN 2,154,419

AUTOMATIC PLANETARY AUTOMOTIVE TRANSMISSION Original Filed Jan. 20, 1936 5 Sheets-Sheet 5 Patented Apr. 18, 1939 UNITED STATES PATENT OFFICE AUTOMATIC PLANETARY AUTOMOTIVE TRAN SDIIS SION Frederick W. Cotterman, Dayton, Ohio, assignor of one-half to Bessie D. Apple, Dayton, Ohio 20 Claims. (01. 14-259) This invention is a division of my copending application Serial Number 59,879, filed January 20, 1936, and relates to power transmission mechanism particularly applicable to motor vehicles.

An object of the invention is to provide a transmission mechanism wherein the most used or middle portion of the driving range of a vehicle will be effected through direct drive, i. e., without the use of any of the gearing in the transmission mechanism.

A second object is to include in the mechanism a single planetary speed reducing gear-set, which may hereinafter be termed the underdrive, which is responsive to speed and torque and which becomes automatically operative when load conditions are such as to either decelerate the vehicle or prevent sufliciently rapid acceleration thereof in direct drive, but which is nevertheless also subject to the will of the operator in that he may, by suddenly changing the amount of applied power by means of the enginethrottle, cause the automatic clutch to act and change from gear drive todirect and vice versa as desired.

Another object is to connect the underdrive gear-set to the engine through a fluid coupling, in order that considerably less reduction in speed need be had through the gear-set, to the end that no engine racing will result in bringing the vehicle from a dead stop through the single speed reduction to a desirable speed for direct drive.

Another object is to include in the underdrive gear-set a plate friction clutch automatically engageable to provide direct drive and render the gear inoperati e, and a jaw brake automatically engageable to providegear drive whenever the plate clutch is disengaged, to the end that the gearing may remain in constant mesh without including in the mechanism any such device as a roller clutch or a spring clutch both of which have been found to be a source of trouble.

Another object is to provide, in the underdrive gear-set, gearing with helical teeth, so angled that the tangential load carried by the gearing causes an end thrust in a direction proper for disengaging the plate clutch, with means to apply the end thrust to the plate clutch to disengage it and keep it fully disengaged as long as the gearing is transmitting any power.

Another object is to provide a resilient means always operative to urge the plate clutch to become'and remain engaged and centrifugal weight means for stressing the resilient means more as the speed increases, the force of the weights being applied to stress the resilient means through a leverage wherein the power arm becomes progressively shorter and the work arm progressively longer as the weight moves farther from its axis of rotation, whereby the stress of the resilient clutch engaging means will increase more nearly as the square root of the R. P. M., instead of as the square of the R. P. M. as is the case where centrifugal means is applied directly or through an unvarying leverage as in common practice, to the end that suificient clutch engaging pressure may be had at the lower speeds without having too great a clutch engaging pressure at the higher speeds.

Another object is to provide, in a gear mechanism which automatically changes from gear drive to direct drive and vice versa, means for making the change from one drive to the other without a time interval between them, the one drive becoming efl'ective before the other drive lets go, to theend that there will be no time between direct drive and gear drive in which there is no drive, as there is in conventional gear shift transmissions.

. Another object is to include in the transmission mechanism a planetary speed increasing gear-set which may hereinafter be designated an overdrive, which may become operative only above a relatively high predetermined speed, to the end that the lesser portion of driving only which is done at very high speeds need be done through this gearing, leaving all normal speeds to be effected without any gearing being operative.

Another object is to provide in connection with the overdrive gearing, such two way driving con-' nections as will insure that the engine is always either driving the behicle or is being driven-thereby, to the end that there will be no overrunning clutches in the mechanism and no free wheeling.

Another object is to provide, in connection with the overdrive gear-set, a direct drive friction clutch normally engaged by a resilient means, whereby the overdrive gearing is kept inoperative, and centrifugal weights operative to overcome the resilient means to disengage the said clutch to permit said overdrive to become operative, with means operated by the thrust of the helical teeth of the gearing to vary the speed at which the weights overcome the resilient means, where- 'by the speed at which the overdrive gearing becomes efiective willbe somewhat higher as the load being overcome is greater.

Another object is to provide an overdrive friction brake wherein one element is secured to the transmission housing which, upon engagement, holds the sun gear of the overdrive gear-set against rotation whereby the overdrive gear-set becomes operative, the helical teeth of the overdrive sun gear being angled to provide an. axial thrust sufficient and in the right direction to hold the said overdrive brake in engagement as long as power is being transmitted through said gearing.

Another object is to provide means through which the same overdrive gear-set may be used.

also as a speed reducing gear-set for reversing the vehicle, to the end that no additionalgears need be provided for this purpose.

. Another object is to provide a manually operable means operative to three positions to provide forward, neutral, and reverse connections between the engine and the vehicle wheels, said means being positioned between the underdrive and overdrive gear-sets.

Another object is to provide a centrifugal means for operating-the overdrive gearing which will insure that when a shift from direct to overdrive or vice versa has once begun to take place the operation will not be interrupted until a complete change from one to the other has occurred.

Another object is to provide in both the underdrive and overdrive mechanisms means for causing the centrifugal weights of a set to all move together to the end that no one weight of a set may move ahead of the others and cause anunbalanced effect.

That I attain these and many other objects and meritorious features will become apparent as the invention is described in more detail and reference is had to the drawings wherein:

Fig. 1 is a longitudinal, horizontal, axial section through the complete mechanism except that a small fragment of each sun gear is shown in full lines to indicate the angle at which the hell- I cal teeth extend.

Fig. 2 is a perspective view of the helical sun gear of the underdrive gear-set, showing also the jaw teeth on the end, which, when effective, secure the sun gear against backward rotation.

Fig. 3 is a perspective view of a member which is secured to the housing of the underdrive gearset and which has jaw teeth which engage the jaw teeth on the sun gear shown in Fig. 2.

Fig. 4 is a fragmentary section taken at 4-4 of Fig. 1 through a hinge pin of one of the centrifugal weights which provide force for stressing the resilient means which maintains clutch engagement.

Fig". -5 is a transverse section taken through Fig. 1 at 5-5 showing the planetary underdrive gear-set surrounded by the plates of the clutch which prevents operation of the gears when it is engaged.

Fig. 6 is a transverse section taken through Fig. 1 at 6-6 showing, largely in end elevation, the centrifugal weights, the spring pressure plate and clutch engaging spider through which the weights act to operate the clutch.

Fig. 7 is a partial longitudinal section, taken on the line '|--'l, through Figs. 5, 6, 12, 13, 14, 15, 16, 1'7, 18 and 19. It shows, in the underdrive mechanism, the clutch, the resilient means for engaging it, the sun gear in position for overcoming the resilient means and maintaining clutclh disengagement and one of the weights for varying the resilient means. In the overdrive mechanism it shows the manually shiftable means for selecting backward or forward vehicle movement, the friction clutch and brake for rotating or stopping the overdrive sun gear, the construction of the overdrive planet pinion carrier and the driven orring gear carrying member. 5

Fig. 8 is a partial section taken through Figs. 5 and 6 at 8-8, showing 'a centrifugal weight with its cam in contact with the spring pressure, and one of the pins for guiding the pressure plate in its axial movement.

Fig. 9 is a partial section taken through Figs. 5 and 6 at 9-9,.showing the planet pinion carrier construction.

Fig. 10 shows diagrammatically the action of the cams of the centrifugal weights on the spring pressure plate. The innermost and outermost positions and four intermediate positions of a weight are shown with corresponding positions of a cam end of the weight. The table of figures gives the spring length for each position of the weight, the corresponding spring stress, and the R. P. M. at which the weights will furnish the said stresses through the several leverages shown.

Fig. 11 is a curve chart plotted from Fig. 10 showing the possible engine power at any speed and what portion of the possible power may be applied at a given speed when indirect drive without forcing the mechanism into gear drive. It also shows by comparison the difference in result obtainable when centrifugal force is applied through a constantly diminishing leverage as compared with direct application.

Fig. 12 is a transverse section taken at I2-|2 of Fig. 1 showing part of the manually operable forward and reverse selective mechanism.

Fig. 13 is a transverse section taken at l3-l3 of Fig. 1 showing another part of the forward and reverse selective mechanism and the plates of the direct drive clutch of the overdrive mechamsm.

Fig. 14 is a transverse section taken at Id-ll of Fig. 1 showing portions of the forward and reverse selective mechanism and the detent mechanism therefor.

Fig. 15 is a transverse section taken at l5|5 of Fig. 1 through the overdrive brake which holds the overdrive sun gear stationary.

Fig. 16 is a transverse section-taken at I6--l6 of Fig. 1 showing the flange of the reversing mechanism and the member which may be selectively made to engage it for reversing the vehicle.

Fig. 1'7 is a transverse, section taken at l'l-l'l of Fig. 1 showing the overdrive gearing.

Fig. 18 is a transverse section taken at l8-I8 of Fig. 1 showing the centrifugal weights which are operative above a predetermined speed to overcome the springs which maintain the direct drive clutch in engagement.

Fig. 19 is a transverse section taken at |9l9 of Fig. 1 showing, mostly in end elevation, the mechanism for compelling all of the centrifugal weights of the overdrive mechanism to move out simultaneously.

Fig. 20 is a fragmentary section taken at 20-20 of Fig. 1 through an overdrive centrifugal weight and spring showing a detent mechanism for holding the weight in its outward position until the speed hasdropped a predetermined amount.

Fig. 21 is a partial detail end view of a; thrust collar operative in engaging the overdrive clutch. A part designated by a given numeral in any one view will not be designated by a different nal 48 is internally splined to receive the externally splined drive shaft 50 of the underdrive gear-set. A ball bearing 52 is provided to take the thrust of the driven element 44. A flywheel cover 54 encloses the flywheel and coupling and supports the transmission housing. The outer face of the cover 54 is closed by the end wall 55 which serves also as the front end closure of the transmission housing. The forward portion of the transmission housing comprises integrally a large cylindrical part 56 and a smaller cylindrical part 51 separated by a central partition 58. The rearward portioncomprises a shell 60 and the ball bearing cap 62,

the underdrive gear-set being contained in the space forward of the partition 58, and the overdrive gear-set and manually operable forward, neutral, and reverse mechanism being contained in the space rearward of the partition and in the rearward portion 60.

The transmission mechanism comprises three shafts all in axial alignment, a drive shaft, an intermediate shaft, and a driven shaft, the fluid coupling being mounted on' the drive shaft, the underdrive gear-set on the intermediate shaft, and the remainder of the mechanism on the driven shaft.

Both of the gear sets herein employed are of the planetary type which comprises a sun gear, several planet pinions surrounding it and meshing therewith, a carrier for supporting the planet pinions for both rotation upon their axes and revolutionabout the sun gear, and a ring gear surrounding and meshing with all of the planet pinions.

In the underdrive gear-set (see Figs. 1 to 11) the splined drive shaft 50 is rotatable in ball bearing 63 supported in the end wall 55. Drive shaft 50 has a. flange to which the ring gear 64 is secured by the rivets 53. Ring gear 64 has helical teeth 66 on the inside of the ring and extemalclutch teeth 68 on the outside, the gear teeth 66 being the driving means for gear drive and the clutch teeth 58 being the driving means for direct drive.

The intermediate shaft I0 is rotatable in roller bearing I2 supported in the end of the drive shaft 50, the other end of the shaft I0 being in turn supported by a roller bearing 14 rotatable in a cage 16 secured by rivets I8 to the center partition 58. The cage I6 is shown in detail in Fig. 3.

Driven shaft has external splines 80 over which the internally splined hub 82 of the planet pinion carrier 84 fits snugly. The carrier 84 supports four circumferentially equally spaced bearing studs 86 having roller cages 88 upon which the planet pinions 90 rotate in mesh with the teeth 66 of the ring gear 64.

The driven friction clutch member 92 has internal clutch teeth 94 (see Figs. 1 and 5) and a forwardly extending hub 96 (see Figs. 8 and 9) which fits over the outer rim of the carrier 84 member 92 whereby said studs have support atboth ends.

v A series of driven clutch plates I00 (see Fig. 5) have external te'eth I02 fitting slidably between the internal teeth 94 of the member 92. A series of driving clutch plates I04 lie between the drivenclutch plates and have internal teeth I06 fitting slidably between the external teeth 68 of the ring gear 64 (see Fig. 5). The outer driven clutch plates I08 are thicker than the remaining .driven clutch plates I00. An internal spring ring H0 is sprung into a groove in the inside of the rim of the driven clutch member 92. This clutch may be called the underdrive clutch and may be broadly designated by the numeral I I I.

The sun gear II2, shown in detail in Fig. 2, is rotatable on a bronze bearing bushing I I4 which is press fitted over the outside of the internally splined carrier hub 82. An integral hub II6 extends rearwardly from the sun gear and is enlarged at II8 to provide a place for openings to contain the balls I and springs I22 (see Fig. 1). A band I24 surrounds the hub to retain the springs in place. The extreme rear end of the hub is formed to compose jaw teeth I25.

Formed integrally around the hub portion I26 of the bearing cage I6 and extending forwardly (see Figs. 1 and 3) are the jaw teeth I28 which correspond to and are engageable with the jaw teeth I 25 of the sun gear. The hub I26 extends into the space left between the inside diameter of the sun gear and the smaller end of the carrier hub 82.

The teeth I21 of the sun gear are helical and are at such an angle that any trangential load carried by the teeth creates an axial thrust in the proper direction to effect engagement of the jaw teeth I25 of the sun gear II2 with the jaw teeth I28 of the bearing cage I6.

Near the forward end of the hub I26 a round bottomed groove I 29 extends completely around it. From this circular groove at equally spaced points around it other round bottomed grooves extend rearwardly and somewhat hellcally, forming the guideways I30 within which the balls I20 act as followers which may move to carry the sun gear II2 rearwardly on the, hub I26. The guideways I30 are slightly deeper at the rear end than they are where they join with the groove I29 so that the pressure on the balls creates a tendency to cause the gear to move rearwardly.

Fig. lshows the sun gear II2 when it is moved rearwardly as far as it will go with its jaw teeth I25 fully meshed with the jaw teeth I28 carried by the bearing cage I6, and with the balls I 20 at the rearward and deepest end of the guideways I30. In this position the sun gear is held against backward rotation as it must necessarily be held to provide gear drive. The sun gear may, however, move forwardly on the hub 82 into the space I32 by drawing the balls I20 forwardly with it into the circular groove I29 whereupon the sun gear is free to rotate forwardly as it must during direct drive. The weight of the balls I20 and the strength of the springs I22 are preferably such that the centrifugal force of the balls becomes greater than the-strength of the springs when the sun gear rotates as much as 600 R. P. M. This proportion will allow ample pressure on the balls inasmuch as the only time the balls need become operative as followers to press downward in the guideways and guide the jaws into engagement is when the sun gear II2 has come to a dead stop and starts'rotating backwardly. I

The balls I20, therefore, never exert any friction on the groove I29 or the guideways I 30 except for perhaps a fraction of a second each time the change from direct drive to gear drive and vice versa is taking place. As soon as the sun gear rotates forwardly in direct drive the balls move radially out ofcontaot with the guideways and groove. 7

The guideways I30 are so located with respect to the teeeth I28, the balls I20 are so located with respect to the teeth I25 that whenever the balls follow the helical paths the mating teeth approach each other in .proper relation for full depth engagement. This is important, for when a jaw brake is employed and permitted to engage without such guiding means it frequently happens that the mating teeth engage with a very shallow hold thus throwing an excessive strain on the points of the teeth which results usually in the engaged teeth slipping off and creating a jerk in the carrying of the load.

The eight sector shaped centrifugal clutch operating weights I34 are each hinged by the pin I36 between a pair of ears I38 extending rearwardly from the friction clutch member 92. Two lateral projections I40 (see Figs. 6 and 7) extend from each Weight I34 and rest upon the outer edges of the ears I38 and limit inward swinging of the weight on its hinge pin. Formed integral with each weight I34 at the back of the hinge is a cam I42 adapted to be operated by the swinging of the weight about its hinge pin. When the weights are swung to their innermost position, that is, with the projections I40 resting on the edges of the ears I38, the heel of the cam I442 rests on a spring pressure plate I46 (see Figs. 1, '7 and 8).

Slightly rearward of the spring pressure plate I46 is the clutch engaging spider I48 having eight radial arms I50 (see Fig. 6). Each arm I50 (see Fig. '7) has forwardly extending therefrom a clutch spring stud I52 and a clutch engaging stud I54. The clutch spring studs are secured in the spider I48 by riveting at I55 and are slidable through the spring pressure plate I56, .the free ends having heads I51.

The clutch springs I58 are held in a substantial initial compression between the heads I56 and the spring pressure plate I46.

The clutch engaging studs I54 are riveted at the rear end of the arms I50, the free end being slidable through openings in the driven clutch member 92. It will be seen that the stress of the springs constantly urges the weights to their in position and at the same time urges the clutch engaging studs I54 forwardly in a direction of clutch engagement. This forward movement is overcome and clutch engagement prevented only by rearward thrust of the helical sun gear when gear drive is in effect. This rearward thrustacts through the clutch throw-out bearing I60 which is held to the clutch engagement spider I48 by a sheet metal cap I6I (see Fig. secured by rivets I63, thereby holding the clutch engaging spider. I48 to its rearward position shown, whereby the clutch engaging studs I54 are held away from the clutch plates I00 and I04. The

clutch is thus held in a fully disengaged position as long as gear drive is in effect.

In the drawings (see Fig.7) the underdrive gear mechanism is shown ingear drive, in which case the clutch engaging studs. I 54 are drawn away from the clutch plate I08 leaving the space I09 into which the plates I00 and I04 may spread. The space I09 becomes wider as the clutch plates wear thinner but provision is made whereby the clutch engaging spider I48 may be moved enough farther by the springs I58 to compensate for such wear as may occur within the life of a motor vehicle whereby no manual clutch adjustment is ever required.

driven clutch member 92.

I As the speed of the vehicle movement rises and falls the weights I34 move outwardly and inwardly thereby moving the spring pressure plate forwardly and rearwardly thus increasing and decreasing the stress of the springs I58. This changing in spring stress takes place with change in the rate of vehicle movement whether gear drive or direct drive is then in eifect. But anytime during gear drive that the speed rises high enough to stress the springs an amount greater than the then existing load isthrusting the sun gear rearwardly, the clutch engaging spider is drawn forward against the sun gear resistance and direct drive will be established. To insure that the weights will move in and out simultaneously, the spring pressure plate is provided with four guide pins I62 (see Fig. 8) which are slidably fitted into openings I64 in the hub 96 of the This prevents any one weight from moving outwardly ahead of the others and thereby creating an unbalanced effect. In any speed torque controlled transmission, gear drive may be made effective below certain speeds by applying engine power sufficient to slip the direct drive clutch. Now inasmuch as the direct drive clutch is maintained in engagement by the force of centrifugal weights which increase their force as the square of the vehicle speed, it follows that where weights are kept small enough to permit gear drive to be brought back into play at speeds above say 30 M. P. H., by application of full engine power, then only one-fourth full engine power may be applied at 15 M. P. H., with out slipping the clutch and effecting gear drive.

It is, however, more desirable to provide a mechanism wherein gear drive may be brought into play at 30 M. P. H., by application of full engine power, but wherein at least two-thirds full engine power may be applied at 15 M. P. H., without reverting to gear drive. This is desirable to permit lower speeds to be effected in direct drive without having the mechanism shift into gear drive when only a reasonable amount of power is being applied.

Conversely it is desirable when in gear drive and acceleration has proceeded until 10 to 15 M. P. H., has been attained, to have the mechanism to change to direct drive at that speed, if the operator, by applying only moderate power, indicates no desire for maximum acceleration. But in conventional speed torque mechanisms, there is far too little weight force at these low speeds to cause a shift to direct drive and the mechanism remains in gear drive even though onlymoderate power is being applied and direct rotating at the lower speeds, then, in 'order'to preventthese weights from applying too great a clutch engaging pressure at the higher speeds,

the leverage through which the weights I34 act on the springs I58 is progressively decreased as the speed of rotation of the weights increase.

This result is obtained by first-positioning the weights I34 with their centersof gravity considerably farther from the transmission axis than Weights are clear in. and the toe of which rests against the spring pressure plate when the weights areclear out.

Fig. 10 shows diagrammatically the movement of the .center of gravity of a weight I34 and the corresponding movements of a cam I42. The point a represents the center of gravity of a weight I34 when it is swung to the in position, the point 1 represents the center of gravity when it is swung to the "out position, and the points b, c, d and e represent intermediate positions.

' the R. P. M. which The points g, h, i, 7 and I represent the positions of the centers of the arcuate working face of the cam I42 corresponding to the several weight positions, that is, when the center of gravity of a weight is at a, the center of the arcuate face of the cam is at y; when the center of gravity of the weight is at b, the center of the arcuate face of the cam is at h, etc. The lines m, n, o, p, q and r represent the positions to which the spring pressure plate I46 has been moved when the center of the arcuate face of the cam has moved to position g, h, i, y, k and I respectively.

From the diagram it will be seen that when the center of gravity of a weight is at a it is 3.797 from the transmission axis about which it rotates, and that it applies its centrifugal force to the spring pressure plate I46 through a lever the power arm of which is .730" and the work arm of which is .375" while when the center of gravity of the weight is, for instance,. in the position e, it is 4.169" from the transmission aids about which it rotates, and it applies its centrifugal force to the spring pressure plate I46 through a lever the power arm of which is .285" and the work arm of which is 1.007". A given force applied by the weight to the spring pressure plate when the weight is clear out is only about $4 aseffective as the same force would be if applied when the weight wasclear in.

The columns of numerical values at the lower end of the diagram Fig. 10 give, from left to right, 1st, the movement of thespring compression plate caused by weight movement to b, c, d, e and f; 2nd, the length to which this movement compresses the springs if the mechanism is in direct drive; 3rd, the length to which thejmovement compresses the springsif the mechanism is in gear drive; 4th and 5th, the forces required to compress the springs to the lengths given in columns 2 and 3 respectively; and 6th and 7th, the weights must make about the transmission axis at their respective .distances therefrom to create the required spring compressing forces through the leverage in effect at the respective positions. f

Fig. 11 is a curve chart wherein the curve .9 is plotted from the numerical values in columns 5 and 7 in Fig. 10 and the curve 1. is plotted from the numerical values found in columns 4 and 6. The curve u is plotted to increase as the square of the R. P. M. and indicates the pounds force which centrifugal weights would apply to maintain'clutch engagement if applied in the usual manner without changing the leverage through which the weights act. ,By curve 8 it may be found that when the underclrlve gear-set is in gear drive and the vehicle speed is 10 M. P. H.,

the weights will be revolving 600 R. P. M. and

will be stressing the-springs with a force of about 120 pounds and that at this speed the engine must apply a force of as much as 60 out of a possible 170 fOOtrDOIlIldS torque to the gears (see values at left of chart), in order to create a rearward sun gear thrust of 1-20 pounds and thereby maintain equilibrium.

It follows that if,at 10 M. P. H., in gear drive, slightly less than 60 foot pounds torque-is applied to the gearing by the engine, a shift up to direct drive will take place. By. the lower curve 11. it may be seen that the application of power to a conventional speed-torque mechanism would have to be reduced to something less than 6 foot pounds to compel the mechanism to remain in direct drive at 10 M. P. H. The result is that, with conventional speed-torque mechanisms, a shift up to the direct drive connection would not likely ever be had at 10 M. P. H., because of the great reduction in applied torque required to cause such a shift up. Such shift up might, however, be had at 10 M. P. H., with conventional mechanism when driving on a considerable down grade.

The same curve s shows that if, when in gear drive, the vehicle is moving 25 M. P. H., the weights will be revolving at 1500 R. P. M. and that the weights will have stressed the springs with a force of 202 pounds and that the engine must apply a torque of as much as 101 out of a possible 170 foot pounds to create a rearward sun gear thrust of 202 pounds to maintain equilibrium and therebymaintain direct drive. It follows that at 25 M. P. H., in gear drive, any reduction in applied torque to less than 101 foot pounds would bring the sun gear thrust to less than 202 pounds and permit the force of 202 pounds, which was being applied to the springs by the weights to cause a shift up to direct drive.

Now the capacity of the underdrive clutch must be such that when it is engaged with a pressure of as much as 200 pounds (see values to right of chart) it will carry the maximum torque input for which the mechanism is designed, namely 1'70 foot pounds. By curve t it may be seen that if direct drive is in effect and the vehicle is moving 25 M. P. H., the weights will be revolving 1500 R. P. M. and stressing the springs with a force of 184 pounds and that in order to slip the clutch and bring in gear drive it will be necessary to apply about 157 foot pounds torque.

From the above it will be seen that, at a vehicle speed of 25 M. P. H., in gear drive, a reduction in torque application to less than 101 foot pounds is. necessary to cause a shift up to direct drive, but if the vehicle maintains this speed at 25 M. P. H., after it has changed to direct drive there must be applied a torque of 156 foot pounds to restore gear drive. This overlap is provided so that too slight changes in torque application will not continually shift from gear drive to direct drive and vice versa and thereby cause undue clutch wear.

The curve 11 represents the maximum in foot pounds torque which may be delivered to the drive shaft 50 by a 90 H. P. engine at the various drive shaft speeds. By comparing the curve '0.

with the curves s and t the percentage of maximum power which must be applied at any speed to prevent a change from gear drive to direct drive and which may be applied at any speed without causinga change from direct drive to gear drive may be seen.

From the curve it may be seen that the maximum engine torque of 170 foot pounds may be applied to the drive shaft 50 when it is rotating asslowly as 450 R. P. M. which, in gear drive, is at a vehicle speed of M. P. H. This is true, however, only where, as in this case, a fluid coupling is used to connect the engine to the drive shaft, because while the drive shaft may be rotating only 450 R. P. M., the engine due to the slippage in the fluid coupling has raced ahead to about 1900 R. P. M. at which speed the engine is able to deliver its maximum torque.

Had a friction clutch been employed instead of a fluid coupling, the maximum torque deliverable at M. P. H., vehicle speed would have been about 132 foot pounds as seen by the dot and dash curve w. The curve 10 is plotted to indicate the torque deliverable by the engine to the shaft 50 when they are'coupled together without slippage and are therefore rotaing in unison. This is the reason why, with a fluid coupling, the lowest gear speed may comprise an engine-to-wheel ratio of 8 to 1 while, where a friction clutch is employed in the same situation, an engine-to-wheel ratio of as much as 11, to 1 is more desirable for the lowest gear speed.

The curve to then actually indicates the maximum torque of the engine when it revolves at the speeds indicated by the figures along the upper edge of the chart which are the speeds required when in gear drive to give the M. P. H., at the extreme bottom of the chart. When, however, the direct drive is in effect, the R. P. M. of shaft 50 for a given M. P. H., will be less, as

indicated by the figures along the lower edge of the chart.

It is therefore necessary when consulting the chart to. ascertain the maximum torque deliverable to shaft 50 when gear drive is in effect to follow the curve 12 through y, but when ascertaining the maximum torque deliverable to shaft 50 in direct drive to follow the curve '0 through :c. This is true for the reason that y is plotted by the figures at the upper edge of the chart while :u is plotted by the figures at the lower edge. By consideration of these curves it will be seen that the curve 1;, by the upper figures begins to fall at 2200 R. P. M., and a: by the lower figures also begins to fall at this same speed, that is the torque which the engine can deliver falls off after an engine R. P. M. of more than 2200 whether the mechanism is in gear drive or direct drive.

The intermediate shaft I0 which serves both as the driven shaft of the underdrive gear-set and the driving shaft of the overdrive gear-set has integral therewith at its rear end the cup III. Different members and combinations of members are connected to or disconnected from the cup III to provide forward direct drive, forward overdrive, neutral, and reverse.

In a planetary gear train of the type shown comprising the three main elements, that is the ring gear usually designated as R, the planet pinion carrier designated as-C, and the sun gear designated as S, it is well known that:

(1) If S is held against rotation, R is made the driver and C is made the driven, as is the case in the underdrive gear-set hereinbefore described, a reduction in speed will be provided.

(2) That if S is held against rotation, C is made the driver and R the driven an increase in speed will be provided.

(3) That if any two members such as S and C are both made drivers while R is made the driven, a direct drive will be provided.

(4) That if C is held against rotation, while S ismade the driver and R the driven, R will rotate in the reverse direction.

(5) That if S only is made the driver while R is the driven and C is left wholly free, C will run idle forward and no driving,connection will be had between the driving and driven members.

The underdrive gear-set hereinbefore described employs the first of the above connections, while the mechanism now to be described makes all of the remaining connections, that is, 2 to 5, some manually, and some automatically, manual means being provided to elect between allowingthe vehicle to stand still, moving it forwardly, or moving it rearwardly, while automatic means are provided to change from direct-forward to overdrive-forward and vice versa at predetemined speeds.

The driven shaft I66, carrying the direct drive, overdrive and reversing mechanism contained in the housing part 51 rearward of thepartition 58 and in the shell 60 is rotatably supported at the front end in roller bearing I68 held in the end of the shaft 10. At the rear end the shaft I66 has external splines I'I0. Closely fitted over these splines is an internally splined hub I12. Hub H2 is drawn against the shoulder I14 of the shaft bythe screw I16 through intermediate numbers I18, I80, I82 and the ball bearing I84 which is the type capable of carrying radial load and axial thrust in both directions. The ball bearing I84 is held in place between the shell 60 and the ball bearing cap 62 by the screws I86.

Hub I12 has eight spokes I88, (see Figs. 7 and 18) extending forwardly from a web I89. This web extends all the way to the outer edges of the spokes. Another smaller web. I9I, (see Fig. '7) is integral with the forward edges of, the spokes midway of their length. The centrifugal weights I85 and springs I81 which control the change from direct drive to overdrive are contained between the webs and spokes, the weights having guide portions I93 and I95 which are slidable in radial slots I99 and 20I in the webs (see Fig. 20). A ring gear I closely surrounds the outer ends of the spokes. (see Fig. 7) which extend radially inward from its inner diameter. Rivets I92 extend through these lugs and through the spokes to secure the ring gears to the spokes, thereby permanently securing the ring gear I90 for rotation with the driven shaft I66.

Rotatable about the shaft I66 is a long bronze sleeve I94 the rear end of which rests against the front face of the hub I12. The forward end is reduced in diameter and on this reduced position is press fitted a manually engageable clutch member I96. Slidably fitted around the sleeve I94 is the long hub I98 of the planet pinion carrier. The forward end of the hub I98 and the rearward end of the driving member I96 are drivably connected-by end splines 200 and 202 respectively (see Figs. 1 and 14). The end splines 200 and 202 enter each other to considerable depth and are slidably fitted whereby the carrier hub I98 has limited sliding movement axially over The ring gear has eight lugs I91 sleeve I94 without losing its driving connection with the driving member I96.

At the rear end of the carrier hub I98 an integral flange 204 extends outwardly. Secured around and to the forward face of this flange by the rivets 206 (see Fig. '7) is the carrier ring 208. This carrier ring is completely cut away at four places2I0 (see Fig. 17) to make room for the planet pinions 2 I2 which are rotatably mounted on roller bearings 2I4 which run on studs 2I6 having one end secured in the flange 204 and the other end in the ring 208. A flange 2I8 extends outwardly at theforward face of the ring 208 and has external clutch teeth 220 around its periphery.

- The sun gear hub 222, which has press fitted into it-abronze bushing 223 rotates freely on the carrier I98. -At the reaw'ardend. of the hub 222 the toothed sun gear 224 is formed. The planet pinion studs 2I6 are so located that the planet pinions 2I2 are in constant mesh with both the ring g ar l98 and the sun gear 224. The teeth of the sun gear 224 are helical, the helix angle being as shown in the small full view fragment Fig. 1. The purpose of the helical teeth is both to provide quiet running and to create'an end thrust proportional to the torque load being transmitted. This end thrust is used to operate the overdrive mechanism in such a manner that an automatic shift to overdrive is made at higher speeds when the torque load being carried is proportionately greater.

Formed integrally around the outside of the, sun gear 222' are the brake plate driving teeth 226. vA series of rotatable plates 228 (see Figs. 1, 7 and 15) have internal teeth 238 which fit slidably over the external teeth 226.

A series of non-rotatable plates 232 inserted into the spaces between the first series have extemai teeth 234. A ring 236 has. internal teeth 238 which fit slidably over the external teeth 234.

At its rear edge the ring 236 is flanged inwardly as at 248, and near its front edge it is flanged outwardly as at 242. The flange 242 is held between the housing parts 51 and 68 by the screws 244 whereby the ring 236 together with the plates 232 are permanently held against rotation. The outside rotatable plate 246 and the outside non-rotatable plate 248 are thicker than the other plates of the brake. An integral flange 249 extends outwardly from the forward end of the sun gear hub 222.

The brake may be broadly designated by the numeral 258 and may be called the overdrive brake because when it becomes engaged and holds the sun gear 224 against rotation, overdrive is in effect. It is held engaged by the end thrust of the sun gear when said gear is under load, the thrust drawing the flange 249 rearwardly until the plates 228 and 232 are compacted between the flange 249 and 248.

This rearward movement of the sun gear 224 compels the planet pinions 2| 2, the carrier flange 284 and ring 288, and the carrier hub I98 to move with it, whereby the end splines 288 and 282 will be engaged to somewhat less depth than shown in the drawings but still of suflicient depth to maintain driving connection between the driving member I96 and the hub I98. This same rearward movement also partly closes the space 252 and thereby enters the planet pinions 2I2 more fully into the ring gear I98.

The thickness of the plates 228 and 232 are, when new, such that when they are fully compacted the space 252 is but partly closed, but if they were worn an amount slightly more than usually results in the average life of a motor vehicle they would not be compacted until the space 252 was entirely closed. This arrangement obviates any necessity for adjustment, because as the plates wear, the compacting flange 249 is moved farther axially by the sun gear thrust to effect engagement.

A cylinder 254 extends forwardly from the flange 249 and has external teeth 256 around its periphery. I A series of driven clutch plates 258 have internal teeth 268 which fit slidably over the teeth 266. The outer driven plate 262 is heavier than the others. A series of driving clutch plates 264 positioned between the driven clutch plates have external teeth 265 and are fltted slidably between internal teeth 266 of the driving clutch drum 268. The outside driving clutch plate 212 is thicker than the others. This clutch may be called the direct drive clutch because it must be engaged to effect direct drive. It may be broadly designated by the numeral 218.

The driving clutch drum 268 is made to always rotate in unison with the cup IN by means of teeth 214 on the rearward end of the cup which extend into the teeth 216 in the forward end of the hub 218 of the driving clutch member 268 (see Fig. 12). These teeth are in permanent engagement. The hub 218 is provided with a bronze bearing bushing 288 runningly fitted to the driven shaft I66. A thrust bearing 282 is interposed between the ends of the teeth 216 and a shoulder 284 on the driven shaft I66, whereby any end thrust due to engagement of clutch 218 will not be transferred to the intermediate shaft 18.

Axially slidable on the outside of the cup. I1I is a shifting collar 286. A clutch ring 288 has internal teeth 298 adapted to slide over the external teeth 292 of the clutch member I96. A series of pins 294 extending, slidably through holes in the hub 218 of the driving clutch drum 268 connect the shifting collar 286 with the clutch ring 288.

A groove 296 in collar 286 receives the shifter fork 298 which has a hub 388 secured to the rod 382 by the screw 384. A slot in the side of the rod 382 receives the lower end of a lever 386 which has bearing at 388 in a hub 3I8 of the housing part 51. A second lever 3I2 is secured to the outer end of the bearing 388 by a nut 3. Forward and backward movement of the upper end 3I6 of the lever 3I2 will move the rod 382 axially in the housing. A Bowde'n wire with push button control on the instrument panel of the vehicle (not shown) or other suitable means may be provided for moving the upper end 3I6 of the lever 3I2.

Bearing for the rod 382 is provided in the housing at 3I8 and 328. A detent ball 322 and spring 324 (see Fig. 14) hold the rod in its several positions. The rear end of the rod has a segment 326having internal teeth 328 adapted to slide over the teeth 228 of the carrier ring 288 to hold the carrier against rotation. A pin 338 extends from the partition 58 and an opening in the fork 298 is slidable over it, whereby the fork is prevented from frictional contact with the bottom of the groove 296.

The direct drive clutch 218 is never disengaged except when overdrive is in efiect. In underdrive, in direct drive forward, in neutral, and in reverse it remains engaged as shown in the drawings. This engagement is effected by the eight heavy coil springs I 81 (see Figs. land 18) which have the outer ends resting in shallow pockets 334 in the rim of the ring gear I98 and the inner ends in deep pockets 336 in the segmental centrifugal weights I85. When the centrifugal force of the weights becomes sufllciently great the springs yield and the weights move radially outward until they rest against the inner side of the rim of the ring gear I98.

The weights I85 are provided at their inner ends with cam parts 348 having sharp noses 342. Corresponding sharp noses 344 are formed integral with a collar 346 (see Figs. 1 and 21). Radial slots 348 formed in thecollar, straddle the spokes I88 whereby the collar is compelled. to rotate with the driven shaft I66 and ring gear I98 which also keeps the cam noses 342 and 344.

posed between the collar 346 and the flange 204.

It will be seen that when the weights I85 are moved radially inward by the springs I81, the noses 342 engage the noses 344 and the collar 346 is moved axially forward, moving with it the carrier flange 204, hub I98, sun gear 224, sun gear hub 222, and flange 249 whereby compacting the plates of the. direct drive clutch 210 and engaging it as shown in the drawings.

The eight springs 348 yield as clutch 210 is being engaged and thereby permit the noses 342- to snap over the noses 344 as shown. In the engaged condition shown in the drawings, the springs 348 act in conjunction with the springs I81 to prevent. the weights I85 from moving overdrive connection to be effected. Four studs:

349 (see Figs. 7 and 13) limit expansion ofthe springs 348. When the plates of clutch 210 are new, the springs 348 will be compressed about as shown, but as the clutch plates wear, the springs 348 willbe compressed as much less as the wear. No adjustment for theclutch 210 is therefore provided. The helix angle of the sun gear 224 is such that'during direct drive forward it creates a rearward end thrust. This thrust also acts in conjunction with the springs I81 to prevent the change to overdrive. Inasmuch as this thrust varies with the torque being transmitted, a shift to overdrive is delayed somewhat longer when the torque being transmitted is greater.

In one side of each weight I85 an opening contains a detent ball 350 and spring 352 which seats the ball in a pocket 354, when the weight is clear out thereby to detain the weights in the out position when they are once out. until a substantial reduction in speed is had. A series of small gears 356, preferably punched from sheet metal are rotatable on studs 358, and are in mesh with each other and with rack teeth 360 out integral with the guide part I95 of the weights (see Figs. 19 and 20). These small gears and racks insure that no one weight may move radially without movement of all of the weights being effected, whereby unbalancing of the mechanism by one weight moving in advance of the others is prevented.

Proportion While thetransmis'sion shown may be designed for an. engine of any ordinary horsepower some indication of the proportion for a given horsepower may preferably be set forth.

With an engine of to H. P. at 3800 to 4200 R. P. M., and a total vehicle weight of around 2600 to 2900 lbs., the proportion of most of the parts may be gotten by taking the outside diameter of the driven clutch-member 92 as 9%" and making all other parts of the mechanism to the same scale. Some of the dimensions which may not readily be gotten by scaling the drawings are as follows:'

The helix angle of the underdrive gear-set should be 23 degrees. The ring gear should have 'a. pitch diameter of 5.432" and have 80 teeth; the sun gearv a pitch diameter of 3.259" and have 48teeth; and the planet pinions a pitch diameter of 1.086 and have 16 teeth.

The rule for ratio when the sun gear is held against rotation, the ring gear is the driver and the planet. pinion carrier the'driven is one revolution of the driven carrier C may be produced by revolutions of the driver R. The underdrive ring,

gear must therefore revolve or 1.6 revolutions to produce 1 revolution of the carrier.

In planetary gearing of the type herein employed the ratio available is confined within narrow limits, being always less than 2 to 1 and more than 1 to 1, the practical limit being reached about 1.75 to 1 for most and 1.25 to 1 for least reduction.

A ratio of 2 to 1 would be obtainable only were it possible to make the diameter of the sun ear and ring gear equal, which would make the planet pinions zero diameter, while the ratio of 1 to 1 would be obtainable only were it possible to make the planets half the ring gear diameter which would require a sun gear of zero diameter.

The underdrive gear-set selected herein is therefore near the practical limit of reduction. This reduction would be insufficient if this gearset were used with an ordinary fly wheel friction clutch, but with the fluid coupling it is ample for the reason that the fluid coupling permits the engine to speed up to its best torque producing speed while the-vehicle speed is still very low. The combination of this type of underdrive gearset with a fluid coupling is therefore considered as a valuable feature of the invention.

The eight sector shaped weights I34 should together weigh about 2.62 lbs., exclusive of the hinge part. The springs I58 should be made of .080" round wire coiled pitch diameter, each have 1'7 turns and a free length of 2.634". The small springs I22 should be of e round wire coiled to pitch diameter, have 4 turns and a free length of /2".

The helix angle of the overdrive gear-set should be 30 degrees. The ring gear should have a pitch diameter of 6.351" and have 88 teeth; the sun gear a pitch diameter of 2.598" and have 36 teeth; and the planet pinions a pitch diameter of 1.876 and have-26 teeth.

When reversing is to be done with a gear-set revolutions of the ring gear backwardly. The

overdrive gear-set will then,'when used, for reversing, provide a reverse ratio of 36/88, i. e., the sun gear must rotate 2.444 turns forwardly to rotate the ring gear one turn backwardly.

When the sun gear only is connected to the driving member and the ring gear is to be nonrotatable, and the carrier is left to rotate-idly, as is the case when the herein described mechanism is in the neutral position shown in thedrawings,

. the rule for ratio is,"1 revolution of the'sun gear will produce revolutions of the carrier, 1. e., if the carrier is left loose, and the ring gear resists rotation, the carrier will idle slowly forward at 88+36 3 l revolution toeach revolution of the sun gear, i. e.,

revolutions of the ring gear. The overdrive ratio than is 88+36 3 1 s8 "22 i. e., one revolution of the driving carrier will produce 1.409 revolutions of the driven ring gear.

The eight segmental weights I85 should together weigh 1.6 lbs. The springs, I 81 should be of round wire coiled to pitch diameter, each having 10 turns and a free length of 2.525". The springs 352 should be of 1 5" A pitch diameter, each have {1 turns and a free length of The springs 348 should be coiled of round wire coiled pitch diameter, each spring have 4 turns and a free length of .765".

A transmission proportioned as shown and used with the power and vehicle weight indicated should be used in conjunction with a rear axle having a ratio of 5 to 1. This will provide engineto-wheel ratios of 8 to 1 direct drive, and 3.548 to 1 for overdrive.

According to present practice the 8 to 1 ratio for low speed would be considered insuflicient, but when coupled with a fluid coupling instead of a clutch this is ample reduction due to the fact that 35 the engine slips the coupling and therefore almost 7 cup member I'll.

instantly rises to its best torque point. The fact is that with a fluid coupling more torque may be applied to the wheels with an 8 to 1 ratio at to 10 M. P. H., than may be applied with a-ratio of 10 or 11 to 1 when an ordinary flywheel clutch is used.

The matter of the relative proportion of the clutches Ill and 210, and brake 250 should be noticed. The mechanism shown 'is'proportioned for 170 foot pounds input. This 170 foot pounds, after being transmitted through the underdrive gears becomes 1.6x 170, or 272 foot pounds at the Now if the clutch 210 had to transmit 272 foot pounds it would ordinarily have to be larger than the clutch Ill. But the clutch 210 is required only to prevent the sun gear 224 from rotatingiorwardly faster than the carrier 204, and the brake 250 is required only to prevent the sun gear 224 from rotating forwardly faster than zero revolutions.

Now if the vehicle were locked against move ment, and the carrier 204 was driven forwardly with a force of 272 foot pounds, so as to force the sun gear 224 to revolve forwardly and thereby 0 slip the clutch 2'|0,,the sun gear would have to revolve forwardly carrying the clutch plates 258 with it at a speed of 1 R+s' ss+36 :g s T 36 9 revolutions of the sun gear forwardly to 1 revolution of the carrier. It follows that the clutch 210 need only be of a size which will transmit of 272 foot pounds, or 79 foot pounds. This is also the maximum which can be imposed on the brake 25 0. a

The clutch 210 proportioned as shown will transmit '79 foot pounds when a minimum axial pressure of 177 pounds is applied to its discs. The springs 348 when proportioned as indicated will round wire coiled for underdrive, to 1 for v applyone and one-half times the above minimum or 266 pounds to maintain engagement.

The brake 250 is proportioned so that the helix angle of 30 degrees specified for the sun gear 224 will create substantially double the axial pressure required to keep the clutch from being slipped by the tangential load on the sun gear when the.

thrust is allowed to engage the brake 250 upon disengagement of "the clutch 21 Operation The operation of the herein described mechanism may be carried out as follows: The top end '3l6 of the lever 3l2 should first be placed in the midway position shown in the drawings whereby the clutch teeth 290 are disengaged from the clutch teeth 292 and the carrier 204 is free to rotate idly.

The underdrive clutch HI and the direct drive clutch 210 being both normally engaged, the sun gear 224 is connected to rotate at the same speed as the shafts 50 and 10. In this state the engine may be started and raced to warm it if desired, without moving the vehicle, because the rotating sun gear 224 and non-rotating ring gear I90 will cause the carrier to rotate idly forward at .29 the speed of the shaft 50, that is, the shaft 50 must rotate about 3% turns to rotate the carrier 1 turn.

The top end 3l6 of the lever 3l2 may now be drawn forward to move the rod 302 rearward to engage the teeth 328 of the segment 326 with the teeth 220 of the carrier ring flange H8. The engine may now be accelerated sufliciently to cause the shaft 50 to be rotated by the engine through the fiuid coupling. The sun gear 224 is still connected through the clutches Ill and 210 and shaft for rotation at the same speed as shaft 50. The ring gear I90 will therefore be driven backwardly at the rate of 1 revolution of the ring gear to 2.44 revolutions of the shaft 50. With a 5 to 1 axle the'engine to wheel ratio of this reversing connection is, 1 revolution of the wheel to 12.22 revolutions o the shaft 50. If while this reversing connection is in effect, the vehicle encounters a considerable resistance to backward movement, and sufficient engine force is applied to overcome it, the underdrive gear-set may become effective whereupon the ring gear I90 will be driven backwardly 1 revolution for each 3.91 revolutions of the shaft 50, The engine to wheel ratio in this case would backwardly .to 19.55 revolutions of the shaft 50 forwardly.

It should be noticed that when the sun gear 224 is thus made the driver for reversing the vehicle, the axial thrust of the helical teeth produces a forward thrust of the sun gear, whereby the greater resistance to reversing encountered by the vehicle wheels, the harder the plates of clutch 210 will be compacted. When resistance to reversing is so great as to bring in the underdrive gearing, and thereby reverse through the high reduction of 19.55 to 1 as above indicated, the plates of clutch 210 will be so compacted as to further compress the springs 348 and allow the endplate 212 to be forced against the end wall of the clutch member 268. This is desirable inasmuch as clutch 210 may be required to carryv be, 1 revolution to the wheel engage the clutch teeth 290 of the ring 288 with the te'eth 292 of the clutch member I96, and disengage the teeth 328 of the segment 326 from the teeth 220 of the flange 2 I8. Inasmuch as the sun gear 224 is still connected by the direct drive clutch 210 to the shaft I0, the entire rotatable mechanism rearward of the partition 58 must rotate in unison, that is the direct drive connection is in effect. The 5 to 1 axle now provides an engine to wheel ratio of 5 to 1.

At any speed now, while direct drive connection is thus made, that the operator applies to the shaft 50 a torque having a value for that speed, which is above the curve t, Fig. 11, he will slip the clutch III and thereby force the underdrive gear-set to become efiective, that is, at 10M. P. H., he may not apply more than 85 foot pounds, (see foot pound values at right of Fig. 11), or at 20 M. P. H., he may not apply Over 137 foot pounds without slipping the clutch and thereby bringing the underdrive gearing into play. After 30 M. P. H., he may apply the maximum of 1'10 foot pounds without slipping the clutch and reverting from direct to underdrive.

Since the clutch III is normally engaged, the sun gear I I2 is rotated forwardly by the ring gear 64 and planet pinlons 90 at the same speed as the clutch. But as soon as a'torque is applied to the clutch III of sufficient value to slip it against the clutch engaging force providedby the weights I34, which is governed by the then existing vehicle speed, the sun gear instantly starts to rotate at less R. P. M., than the clutch. When the clutch slips an amount which permits the ring gear 64 to revolve 1.6 times as fast as the carrier 84, the sun gear will have been brought to a non-rotative state.

At the slightest increase in slip of clutch III, the sun gear H2 starts to rotate backwardly, whereupon the helical teeth I21 which up'to now drew it axially forward into the space I32 now starts it axially rearward. As this occurs the helical teeth I21, the balls I20 and guideways I30 and the jaw teeth I25 and I28 all cooperate to move the sun gear rearwardly and guide the law teeth I25 and I28 into correct engagement.

When the jaw teeth engage and the gear load is taken up, the jaw teeth are forced by the load acting on the helical teeth to full depth engagement and thereby, through the thrust bearing I80, fully disengage the clutch III so that there will be no partial engagement and consequent drag,

Any time and at any speed the operator may release the accelerator sufficiently to cause the rearward load created thrust to be less than the forward weight created thrust and thus allow the sun gear to move axially forwardabout This does not instantly change from underdrive to direct drive because when the sun gear has been pushed forwardly about 4;", the studs I54 press the friction clutch discs I00 and I04 together. The jaw teeth I25 and I28 being about /4" long are not out of mesh and therefore momentarily continue the gear drive in effect, but the friction between the rubbing clutch discs although not great at the first touch, nevertheless takes some of the load off of the gearing.

When it takes some of the load off of the gearing the rearward thrust on the sun gear I I2 is Just that much less, and being less permits more of the clutch engaging pressure of the springs I58 to be applied to the discs, which, rubbing harder, takes more load off of the gearing. This is repeated over a period of several seconds where! upon enough of the spring pressure is applied to the discs to allow the driving discs I04 to revolve more nearly at the same speed as the driven discs I00 than the ratio of 1.6 to 1 of the gears whereupon all of the load is removed from the sun gear H2 and it is rotated clockwise.

As soon as this occurs, the jaw teeth I25 and I28, the guideways I30 and the helical teeth I21 all cooperate to move the sun gear forwardly and completely disengage the jaw teeth. The helical teeth alone will keep them disengaged as long as the sun gear II2 rotates forwardly, which is as long as direct drive is in effect.

Instantly the sun gear rotates forwardly, if the speed has been raised to as much as 10 M. P. H., the followers I20, which have been pressing downwardly in the groove I29 and guideways I30 while the sun gear was non-rotative, now rise against the springs and remove the friction between the followers and the guideways and oove.

It is however, possible to start from zero M. P. H., and accelerate the vehicle to a high speed without bringing the underdrive gearing in at all, but the torque applied in such a case to shaft 50 at zero M. P. H., would have to be so low that acceleration would be very slow.

In starting from a dead stop, therefore, the operator will almost invariably apply enough torque to bring in the underdrive gearing. In sections where 15 M. P. H., is the limit of speed, some drivers, in starting from a dead stop may apply maximum torque as indicated by the curve 1;, Fig. 11, and thereby bring in the underdrive gearing, then accelerate by maximum torque to 15 M. P. 11., then reduce the torque to foot pounds or less which would cause a change to direct drive, and thereafter so regulate the applied torque as to keep down to 15 M. P. H., until another stop was required.

In sections where no speed limit isimposed, the driver, starting from a dead stop, may apply full torque as indicated by the curve 12 to bring in the underdrive gearing, then keep the torque at the highest possible value. After a speed of 2200 R. P. M. of the engine, the maximum torque will decrease as seen in curve 11. At 3840 R. P. M. of the engine, or 40 M. P. H. in underdrive, the torque will have fallen off from to 122 foot pounds.

This 122 foot pounds creates a sun gear thrust of 240 pounds tending to maintain underdrive in effect, (see values at left of Fig. 11). By reference to curve s it will be seen that at 3840 R. P. M.,

or 40 M. P. H., in underdrive, the weights I30 have energized the springs I58 to such an extent that they are providing 240 pounds force tending to engage the clutch III. Any slight increase in speed above 40 M. P. H., in underdrive, will force a shift to direct drive. It will therefore be seen that a driver may, in starting from a dead stop, accelerate to. a high speed without usin underdrive if given sufiicient time; he may accelerate to 10 to 15 M. P. H., in underdrive then shift to direct by lowering his applied torque; he

may then continue at this speed in direct or accelthen accelerate .maintain it up to any speed 2,104,419 soon as possiblahe could, by applying torque in excess of 137 foot pounds change to underdrive,

to M. P. H., whereupon the shift to direct would take place. If, however, the vehicle is once moving at a speed of as much as 30 M. P. H., in direct drive, no return to underdrive may be effected except by lowering the speed, becauseat 30 M. P. H., in direct drive, the weights I will energize the springs I58 with a clutch engaging force of 200 pounds (see curve t) and clutch I I I is so designed that when it is held engaged with a force of 200 pounds it will carry the maximum torque of 170 foot pounds (see values at right of Fig. 11). The operator may, therefore, voluntarily bring in underdrive at any speed under 30 M. P. H., and may not to exceed 40 M. P.H. The engine speed of 3840 R. P. M., necessaryto bring the vehicle speed to 40 M. P. H., in' -underdrive is not injurious inasmuch as enginesofvthis class have an operating range up to 5000-R11P. M. When the direct drive clutch III engages: at 40 M. P. H,, the engine will drop in speedfrom3840 to 2400 R. P. M., (see values at topand'bottom of Fig. '11).

Having thus employed underdrive to overcome unusual resistance, as in accelerating the vehicle,

or in climbing an unusual hill, the operator will maintain direct drive forall ordinary driving.

But with the 5 to 1 axle ratio indicated as suitable for use with the herein mechanism the engine would again berevolving 3000 R. P. M., when a speed of M. P. H. is reached in direct drive, 3600 R. P. M. at M. P. H., 4200 R. P. M. at'70 M.P. H., and 4800 R. P. M. at 80 M. P. H., and while it would'be possible to drive in direct with these engine'speeds it is far more desirable after a speed of 50 M. P. H. has been passed to change to the overdrive mechanism herein shown, in which case a speed of 50 M. P. H., is maintained at 2129 engine R. P. M. 60 M. P. H., at 2555 R. P. M., 70 M. P. H., at 2981 R. P. M., M. P. H., at 3406 R. P. M., and 90 M. P. H., at 3832 R. P'. M., the latter engine speed being still within a limit which is not destructive.

Inasmuch as the springs 348 constantly, through intermediate parts, press the nose 3 of the weight holding collar 346 over the outer surface of the nose 2 of the weights I85, with a force of 266 pounds as before stated, and thereby keep the direct drive clutch 270 engaged, the weights I are necessarily so proportioned that they develop 266 pounds more centrifugal force outwardly than the springs I8I'exert inwardly, at 50 M. P. H., 'hereby a shift to overdrive takes place at that speed. But this shift only takes place at 50 M. P. H., if the 266 pounds force of the springs 348 is not augmented by the rearwardaxial thrust of the sun gear 224 which may, when under full load, be as much as 264 pounds-when the gear is made with the helix angle indicated.

It follows that the operato at 50 M. P. H., may momentarily reduce his applied torque to zero, whereupon the weights I85 will, by first compressing the springs 348, move to their out positions and be held there by the detent balls 350 and springs 352. As this occurs, the springs 348 will expand to the limit imposed by the studs 8, but as long as the applied torque is zero and the ve-. hicle thereby drives the engine the sun gear will exert a forward thrust and the discs of the clutch 210 will remain under pressure. when power is again applied, the sun gear thrust will be rearward whereby the overdrive brake 200 will become engaged.

in underdrive at about 3500 R.

but he may not I M. P. H., the speed at which he would have to maintain it with less total horsepower.

"force of the detent When, however, the operator does not momentarily reduce his applied torque to zero at 50 M. P. H., but instead, let us say, applies full torque, a shift up to overdrive will be delayed until an increase of about 8 M. P. H., is made due to the fact that the applied torque causes a rearward thrust of the sun gear which augments the force of the springs 348 and thereby makes it necessary that a greater surplus of force be generated by the weights I 85 over that of the springs I8'l,before the weights will move to their out position.

The curve w,y, Fig. 11, shows that the torque of an engine as herein specified begins to become less at 2000 R. P. M. From it may be determined that the horsepower, that is, the torque times the speed at which that torque is had begins to drop P. M. In direct drive 2000 engine R. P. M. drives the vehicle about 33 M. P. H., while 3500 R. P. M. drives the vehicle about 58 M. P. H.

It will be seen that there is provided a means whereby the operator, by applying maximum torque, may hold the direct drive connection in effect only as long as a speed is not exceeded at which the H. P. begins to diminish. With the mechanism proportioned as indicated he may shift to overdrive at 50 M. P. H., if he so desires, maintain direct drive beyond 58 When the mechanism isin overdrive, and the vehicle speed falls to 44 M. P. H., the outward force of the weights I85 is as much less than the inward force of the springs I01 as the holding springs 352 and the balls 350 whereupon the weights start in. If the operator at this speed happens to momentarily decrease the applied torque to zero, the difference of the spring force over the weight force will at once force the-noses 342 past the noses 3, whereupon the direct drive clutch will be engaged. If, however, no release of applied torque occurs, a further reduction, the amount depending on the torque being applied will be required before the force of the springs I81 exceeds the force of the weights I85 sufliciently to engage the direct drive clutch.

If, while overdrive is thus in eifect, and the speed has fallen below 42 M. P. H., the maximum torque is applied, the underdrive gearing will be brought into play while the overdrive gearing is still operative thereby to increase the power without having shifted out of overdrive.

The advantages of the mechanism herein disclosed may be briefly summarized as follows:

By employing, in connection with the mechanism shown, an axle having the relatively low pinion-to-wheel reduction of 5 to 1, in combination with a fluid coupling, a speed range of 0 to 58 M. P. H., may satisfactorily be had in direct drive.

More rapid acceleration may be had through the underdrive gearing which gives an engine-' to-wheel ratio of 8 to 1, said underdrive gearing being made effective by momentarily applying a considerable proportion of the full engine torque,

where no overdrive is provided yet with 3.548 to 1 overdrive ratio for speeds above 50 M. P. H., the 5 to 1 direct drive ratio is preferable.

While the operator may control within limits, the speed at which the automatic shift from underdrive to direct drive occurs, and the speed at which the automatic shift from direct drive to overdrive occurs, he may not delay a shift in either case much beyond the engine speed at which maximum horsepower may be developed.

The changes from one ratio to another all are made without an interval during which there is no connection between the engine and the wheels, that is, the mechanism does not have free wheeling characteristics.

In a co-pending application, Serial No. 26,765, filed June 15, 1935, there is shown an underdrive gear box having planetary gearing of the same general nature as the present invention. The two structures, however, differ in several important respects, one difference being that in the co-pending application the main clutch, i. e., the large friction clutch is normally open to allow gear drive, and closes only to change to direct drive when the centrifugal weights generate enough force to overcome a set of clutch disengaging springs plus the torque reaction on the sun gear. This torque reaction varies with the load being carried by the gears, and therefore the speed at which direct drive comes into play varies with the power being transmitted.

In the present invention, the large friction clutch is always closed unless sufficient load is applied thereto to slip it, whereupon it is held open by the gear load until the centrifugal weight force becomes greater than the gear reactions. I

A further difference between the copending and present invention is that, in the copending structure, the centrifugal weights act through leverage means wherein the effective length of the power arm progressively decreases as the weights move out, but the work arm remains constant, while in the present invention the effective length of the power arm progressively decreases and the efiective length of the work arm progressively increases as the weight arms move out, resulting in a far more rapid falling off in the ratio between weight power generated and weight power applied in the present than in the copending structure.

In another co-pending application, Serial No. 94,053, filed August 3, 1936, there is shown a planetary gear mechanism having the same general characteristics as that herein shown, except that the main friction clutch of the present invention is replaced by a jaw clutch which releases on overload and has a synchronizing mechanismto prevent jaw clutch clatter when it is engaged or disengaged.

Claims in the present invention are therefore aimed to distinguish from those in the two copending applications in some of the particulars pointed out.

The proportions of the parts herein givenare solely for the purpose of assisting'those skilled in the art to adapt the mechanism to engines of varying power and vehicles of varying weight and as such are not intended to limit the scope of the invention. To define this scope, I claim:

1. In a power transmission mechanism, a driving member, a driven member, a friction clutch for connecting said members, gearing for drivably connecting said members whenever said clutch is disengaged, a spring under stress, a

spring compressing member positioned to receive the spring reaction at its one end, a centrifugal weight operative upon increase in speed to move said spring compressing member to further compress said spring, a clutch engaging member positioned to receive the spring reaction at its other end, said clutch engaging member being normally moved by said spring reaction to a position which holds the clutch engaged, and a torque responive means operative by load on said gearing to move said' clutch engaging member oppositely to hold said clutch disengaged, whereby clutch disengagement is always automatically terminated by generation of weight force in excess of the torque reaction of the gear load.

2. Power transmission mechanism comprisin a driving member, a driven member, gearing for drivably connecting said members, a friction clutch adapted to keep said members connected I directly whenever said gearing is'inoperative, a spring under stress, a spring compressing member positioned to receive the spring reaction at its one end, a centrifugal weight operative upon increase in speed to move said spring compressing member to further compress said spring, a clutch engaging member positioned to receive the spring reaction at its other end, said clutch engaging member being normally moved by said spring reaction to a position which holds the clutch engaged, and helical teeth on one of said gears operative to move said gear axially underload against said clutch engaging member thereby to move said clutch engaging member in the direction to hold said clutch disengaged, whereby clutch disengagement is always automatically terminated by generation of weight force in excess of the then existing axial reaction of said helical gear.

3. The combination, in power transmission mechanism, of a driving member, a driven member, a friction clutch normally connecting said members, gearing for drivably connecting said members and disengaging said clutch upon overloading of said clutch, a spring under stress, a spring compressing member adapted to receive the spring reaction at its one end, a centrifugal weight operative upon increase in speed to move said spring compressing member to further compress said spring, a clutch engaging member adapted to receive the spring reaction at its other end and transfer it to the clutch to hold the clutch engaged, overrunning means for said gearing whereby said bearing may runv without load while said clutch remains engaged, and torque responsive means associated with said gearing operative, when said clutch slips ,due to overload and said overrunning means ceases overrunning and said gears take up the load, to move said clutch engaging member oppositely and thereby completely disengage said clutch, whereby said clutch remains disengaged only so long as said gear load produces a torque reaction in excess of the than existing weight force.

1. Power transmission mechanism comprising,

in combination, a driving member, a driven mem-' ber, a clutch connecting said members, a spring under stress normally holding said clutch engaged, gearing for drivably connecting said members when said clutch yields to overload, means for holding said clutch disengaged only so long as said gearing is driving a spring compressing member receiving the spring reaction at one end, a clutch engaging member receiving the spring reaction at the other end and applying it to the clutch to maintain engagement, a centrifugal weight operative upon increase in speed to move said spring compressing member to further increase said spring stress, and leverage means acting between said weight and said spring compressing member the power arm of which gets progressively shorter and the work arm progressively longer as the weight gains in speed and moves farther from the axis of revolution.

5. Power transmission mechanism comprising, in combination, a driving member, a driven member, a clutch connecting said members, a spring under stress normally holding said clutch engaged, gearing for drivably connecting d members when said clutch yields to overloa ,a spring compressing member receiving the spring reaction at one end, a clutch engaging member receiving the spring reaction at'the other end and transferring it to the clutch to maintain engagement, a centrifugal weight operative upon increase in speed to move said spring compressing member to further compress said spring, leverage means operative between said weight andsaid spring compressing ,member the power arm of which gets progressively'shorter and the work arm progressively longer as the weight moves farther from the axis of revolution, and torque responsive means operative by load on said gearing to move said clutch engaging memberoppositely from the direction in which it is moved by said spring, to thereby hold said clutch disengaged so long as said gearing is under load.

6; The combination, inpower transmission mechanism of the character described, of a driving member, a driven member, a clutch directly connecting said members, a spring under continuous stress normally holding said clutch engaged, a gear on the driving member, a sun gear, planet pinions on the driven member in mesh with both said gears, said gearing being adapted for gear connecting said members whenever said engaging member to disengage said clutch only clutch yields to overload, a member receiving the spring reaction at one end, a clutch engaging member receiving the spring reaction at the other end and transferring it to the clutch to maintain engagement, and torque means comprising means to prevent backward rotation of said sun gear,

under load, and helical teeth on the sun gear operative under said load to thrust said sun gear axially against said clutch engaging member and thereby remove the clutch engaging pressure applied by said spring, whereby said clutch is automatically reengaged whenever the axial thrust of said sun gear falls below said spring stress.

7. In power-transmission mechanism of the character described, a driving member, a driven member, a clutch connecting said members, a spring under stress normally holding said clutch eng ged. a gear on the driving member, a sun gear, planet pinions on the driven member in mesh with both saidgears, said gearing being adapted for gear connecting the driving and driven members when said clutch yields to overload, a spring compressing member receiving the spring reaction at one end, a clutch engaging member receiving the spring reaction at the other end and transferring it to the clutch to keep it engaged, a centrifugal weight operative upon increase in speed to move said spring compressing member to further compress said spring, and torque means comprising helical teeth on the sun gear operative by load'on the said sun gear to thrust said sun gear axially against said clutch while said gears are under load, whereby said axial thrust falls below the stress than being supplied to said spring by said weight.

8. The combination, in power transmission mechanism of the character described, of a housing, a driving member, a driven member, a clutch normally connecting said members directly, a spring under stress holding said clutch engaged when the mechanism is not operating, a gear on the driving member, a sun gear, a planet pinion on the driven member in mesh with both said gears, a jaw element on the sun gear, a jaw element on the housing, whereby said gearing is adapted to gear connect the driving and driven members by engagement of said jaw elements to hold said sun gear against rotation when said clutch yields to overload, a member receiving the spring reaction at one end, a clutch engaging member receiving the spring reaction at the other end and transferring it ,to the clutch to hold it engaged, and torque means comprising helical teeth on' the sun gear operative by load on said sun gear to thrust said sun gear axially against said clutch engaging member to disengage said clutch and to engage said jaw elements, whereby said clutch remains disengaged only so long as said gear load creates an axial thrust in excess of said spring stress.

9. Power transmission mechanism of the character described, having in combination, a housing, a driving member, a driven member, a clutch normally connecting said members direct- 1y; a spring under stress holding said clutch engaged, a gear on the driving member, a' sun gear, planet pinions carried by the driven member in mesh with both said gears, a one way jaw brake element on the sun gear, a one way jaw brake element on the housing whereby said gearing is adapted to gear connect said driving and driven members by engagement of said .iaw brake elements to hold the sun gear against backward rotation whenever said clutch yields to overload, a spring compressing member receiving the spring reaction at one end of the spring, a clutch engaging member receiving the spring reaction at the other end of the spring and applying it to the clutch to keep it engaged, a centrifugal weight operative by increase in speed to move said spring compressing member to further compress said spring, and torque means comprising helical teeth on the sun gear operative under torque load to thrust said sun gear axially to move said clutch engaging member against the force of the spring to disengage the clutch and engage the said jawbrake elements, whereby gear drive is automatically discontinued wheneverthe centrifugal weight stresses the spring more than the torque load thrusts the sun gear 10. The combination in power transmission mechanism, of a housing, a driving member, a driven member, a clutch normally connecting said members, a spring under stress holding said clutch engaged, a ring gear on the driving member, a sun gear, planet pinions carried on the driven member in mesh with the ring gear and sun gear, a jaw brake element on.the sun gear, a jaw brake. element on the housing, whereby said gearing is adapted to gear connect the driving and driven members by engagement of said jaw brake elements to hold said sun gear against backward rotation when said'clutch becomes disengaged, a member receiving the spring reaction at one end, a clutch engaging member receiving the spring reaction at the other end and applying it to the clutch to maintain engagement, torque means comprising helical teeth on the sun gear operative by load on said sun gear to thrust said sun gear axially against said clutch engaging member to disengage said clutch and to engage said jaw brake elements, and guide means to guide the jaws of one jaw brake element into engagement midway of the jaws of the other jaw brake element, said clutch being operative to be held out of driving relation only so long as the said axial thrust which is holding said jaws engaged does not fall below said spring stress.

11. In a power transmission of the character described, the combination of a housing, a driving member, a driven member, a friction clutch connecting said members directly, spring means under stress holding said clutch engaged, an internal ring gear on the driving member, a sun gear concentric with said ring gear, planet pinions carried by the driven member in mesh with the ring gear and sun gear, a one direction jaw brake element on the sun gear, a mating jaw brake element on the housing, whereby said gearing may gear connect the driving and driven members by engagement of said jaw brake elements to hold said sun gear against backward rotation when said friction clutch slips from overload, a spring compressing member receiving the spring reaction at one end, a clutch engaging member receiving the spring reaction at the other end and applying it to hold the friction clutch engaged, centrifugal weights operative by increase in speed to move said spring compressing member to further stress said spring, said weights having a power arm which progressively declutch remains disengaged only so long as the axial thrust exceeds the stress applied to the spring means by the weights. I

12. The combination, in power transmission mechanism, of a housing, a driving member, a driven member, a friction clutch connecting said members directly, spring means under stress holding said clutch engaged, an internal gear on the driving member, a sun gear concentric with the internal gear, planet pinions carried on the driven member in mesh with the internal gear and the sun gear, a one direction jaw brake element on the sun gear, a mating jaw brake element on the housing, whereby said gearing may gear connect the driving and driven members by engagement of said jaw brake elements to hold said sun gear against backward rotation when said friction clutch slips from overload, a spring compressing memberj receiving the spring reaction at one end, a clutch engaging member receiving the spring reaction at the other endand applying'it to the friction clutch to hold it engaged, centrifugal weights operative by increase in speed to move said spring compressing member to further stress said spring means, said weights applying their force to the spring compressing member through leverage wherein there is a power arm the effective length of which progressively decreases and "a work arm the effective length of which progressively increases. as the weights move farther from the axis about which they revolve, torque means comprising helical teeth on the sun gear operative to thrust said sun gear axially to move said clut'ch engaging member against the force of said spring means to disengage the friction clutch and engage the said jaw brake element, and helical guide and follower means operative to guide the jaws of one v of the jaw brake elements into engagement midway of the jaws of the other jaw brake element when said jaw brake elements engage, said friction clutch being thereby held disengaged only so long as the said axial thrust exceeds the weight force being applied to the spring means.

13. An underdrive gear mechanism comprising, a driving member, a driven member, a friction clutch for connecting said members to revolve in unison, a gear on the driving member, planet pinions in mesh with said gear, a planet pinion carrier on the driven member, a sun gear in mesh with said planet pinions, said sun gear having limited axial movement to effect gear connection when said friction clutch slips from overload, a variably stressed resilient means normally holding the friction clutch engaged, centrifugal weights operable outwardly by increase in rotative speed, lever means operable by said weights to stress said resilient means, the effective power arm of said lever means becoming progressively shorter and the effective work arm progressively longer as the weights move farther with the sun gear brakemeans, helical gear teeth on the sun gear angled to create an axial thrust under load operative to engage said sun gear brake means with the non-rotatable brake means and operative to remove the force of said resilient means from said friction clutch to completely disengage said friction clutch and to hold said friction clutch disengaged only so long as the centrifugal weights stress the resilient means with a force inexcess of the end thrust of the sun gear due to load.

14. An underdrive gear mechanism comprising, a driving member, a driven member, a friction clutch for connecting said members to revolve in unison, speed reducing gearing for connecting said members only when said friction clutch slips from overload, one of said gears being movable axially to effect gear connection, a variably stressed resilient means normally holding said friction clutch engaged, speed responsive means operative to increase the stress of the resilient means at a rate which is less than directly proportional to the increase in speed, helical teeth on the axially movable gear angled to create an axial thrust under load operative to move said gear axially to effect gear drive connection and to remove the force of said resilient means from said friction clutch to completely disengage said clutch and to hold the force of said resilient means from said friction clutch to maintain disengagement thereof only as long as the speed responsive means does not stress the resilient means in excess of the said axial thrust of said one gear.

15. An underdrive gear mechanism compris-- cess'of said axial force.

16. An underdrive gear mechanism comprising, a driving member, a driven member, a friction clutch for connecting said members directly, speed reducing gearing for connecting said members operative only when said friction clutch yields to overload and the driven member revolves at less speed than the driving member, means to hold said clutch disengaged only so long as said gearing is driving, a variably stressed resilient means applied to said friction clutch to keep it engaged, speed responsive means for increasing the stress of said resilient means, and leverage means for stressing said resilient means, by saidspeed responsive means the effective length of the power arm of which progressively diminishes and the effective length of the work arm of. which progressively increases with the increase in speed.

17. An underdrive gear mechanism comprising, a driving member, a driven member, a friction clutch for connecting said members directly, speed reducing gearing for drivably connecting said members only when said friction clutch slips due to overload, means operable by said slip to effect said driving connection,- a variably stressed resilient means, normally holding said friction clutch engaged, and speed responsive means operative to increase the stress of the resilient means at a rate which is less than directly proportional to the increase in speed, said resilient means being automatically operable to reengage said clutch when said gearing ceases dr ving. V

18. Power transmission mechanism comprising, a driving member, a driven member, a friction clutch for connecting said members directly, speed reducing gearing operable into load carrying relation by slippage of said friction clutch due to overload, a normally stressed resilient means appliedto said clutch to keep it engaged, means operable by load on said gearing for overcoming said resilient means, centrifugal means for stressing the resilient means, and compensating means for modifying the force of the centrifugal means, whereby said resilient means is further stressed by increase in speed at a rate which is less, than directly proportional to the speed increase, said clutch being automatically reengaged uponoperation of said gearing out of load carrying relation.

19. Power transmission mechanism comprising, a driving member, a driven member, a friction clutch for connecting said members directly, speed reducing gearing, gear control means operable by slippage of said clutch for causing the driving member to drive the driven member thru said gearing, means commensurate with the gear load holding the clutch disengaged, a normally stressed resilient means applied-to said clutch whereby it reengages as soon as the force of said gear load becomes less than the stress of said resilient means, centrifugal means for stressing the resilient means, and compensating means between the resilient means and the centrifugal means, adapted to modify the rate of increase of the stressing force of the centrifugal means from the square of the revolutions to less than directly proportional to the revolutions.

20. Power transmission mechanism comprising, in combination, a driving member, a driven member, a friction clutch for connecting said members, a stressed resilient means holding said clutch engaged, mechanism to increase the stress of the resilient means as the speed increases but at a rate of increase which is less than directly proportional to the speed increase, speed reducing gearing operative to drivably connect the driving and driven members only when said friction clutch is inadequately engaged to carry the load without slippage, means made operative by said slippage to efiect said gear drive connection, and means made operative by torque load on said gearing to wholly disengage said clutch.

FREDERICK W. COfII'ERMAN. 

